﻿//using System;
//using System.Linq;
//using System.Linq.Expressions;

//namespace Jinndev.DB {

//    public static class PredicateBuilder {

//        /// <summary>
//        /// 机关函数应用True时：单个AND有效，多个AND有效；单个OR无效，多个OR无效；混应时写在AND后的OR有效
//        /// </summary>
//        /// <typeparam name="T"></typeparam>
//        /// <returns></returns>
//        public static Expression<Func<T, bool>> True<T>() { return f => true; }

//        /// <summary>
//        /// 机关函数应用False时：单个AND无效，多个AND无效；单个OR有效，多个OR有效；混应时写在OR后面的AND有效
//        /// </summary>
//        /// <typeparam name="T"></typeparam>
//        /// <returns></returns>
//        public static Expression<Func<T, bool>> False<T>() { return f => false; }

//        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) {
//            InvocationExpression invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
//            return Expression.Lambda<Func<T, bool>>(Expression.Or(expr1.Body, invokedExpr), expr1.Parameters);
//        }

//        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2) {
//            InvocationExpression invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
//            return Expression.Lambda<Func<T, bool>>(Expression.And(expr1.Body, invokedExpr), expr1.Parameters);
//        }

//    }

//}
